Streptococcus Pneumonia Flashcards
1
Q
Streptococcus Pneumonia
Overview
A
- G +
- Cocci, pairs or chains
- Facultative Anaerobe
- Catalase -
- Alpha Hemolysis
- Virdans Group
2
Q
S.pneumonia
Encounter
A
- Normal flora of nasopharynx and oropharynx
3
Q
S.pneumonia
Entry
A
- Endogenous source
- Spread to lung, sinuses, ears, or meninges
4
Q
S.pneumonia
Spread
A
- Person to person through respiratory droplets
- Many people are asymptomatic carriers.
5
Q
S.pneumonia
Multiplication
A
- Resist phagocytic clearance by capsule
- xtcl growth on mucous membranes of the respiratory tract or in blood
6
Q
S.pneumonia
Damage
A
- Pneumonia
- Sinusitis
- Otitis media
- Bronchitis
- Meningitis
- Bactermia
7
Q
S.pneumonia
Diagnosis
A
- Gram stain of sterile tissue or fluid sample
- BAP Culture
8
Q
S.pneumonia
Treatment
A
- Sensitive penicillins/cephalosporins
- Resistance is on rise*
- Prevention by accination (to capsular polysaccharide)
9
Q
**S.pneumonia Characteristics **
A
- Encapsulated w/ a complex polysaccharide capsule (90 different serotypes)
- No M protein on its surface.
- The cell wall contains both lipoteichoic and teichoic acids.
- Teichoic acids extend beyond capsule to be exposed, called C-polysaccharide.
- Lipoteichoic acid called F-antigen.
- Both contain phosphorylcholine which is a unique
- Requires choline to grow
- Phosphorylcholine activates cell wall hydrolase which allows breaking of cell wall and filling in with new cell wall biomass
- Without active hydrolase will stop growing
- Tissue destruction is mediated primarily by host defense systems.
10
Q
S. pneumoniae Colonization
A
11
Q
**S.pneumonia **Virulence Factors
Phosphorylcholine
A
- Important role in pathogenesis.
- Can bind platelet active factor (PAF) receptors expressed on the surface of endothelial cells, leukocytes, platelets and tissue cells.
- Contributes to the acute inflammation response
- Allows bacteria invasion of cell, bacteria is put in a vacuole that is trafficked to the other side of the cell and released.
12
Q
S.pneumonia Virulence Factors
Phosphorylcholine Surface Proteins
A
- CbpA: involved in PAF recptor internalization of bacteria.
- PspA: Protective antigen, inhibits complement mediated opsonization.
- PspC: an adhesin targetting host cell secretory component protein (SC)
- LytA, B and C: autolysins that kill the bacteria upon stationary phase growth and contribute to the inflammation response.
13
Q
S.pneumonia Virulence Factors
**IgA Protease **
A
- IgA protease: host IgA traps the bacteria in mucose,
- IgA protease cleaves antibody allowing escape from mucous.
- Cleavage of IgA results in capsule disuruption, freeing phosphorylcholine (ChoP in figure) to bind to PAF recpetor.
- allows tocircumvent removal
14
Q
S.pneumonia Virulence Factors
Pneumolysin
A
- pore forming cytotoxin that binds host cell cholesterol
- Kills ciliated epithelial cells
- allows to circumvent removal
- can also bind the Fc Region of human IgG
- Binding activates the Classical Complement pathway
- More inflammation
- Complement cascade lyses cell.
15
Q
S.pneumonia Virulence Factors
Lack of Catalase
A
- generates large amount of H2O2.
- Reactive oxygen species can lead to tissue destruction.
16
Q
S.pneumonia Virulence Factors
Techoic Acid
A
- Phoshporylcholine in techoic acid allows it top bind PAF receptor on endothelial cells, WBCs, RBCs, and platelets
- The bound techoic acid is recognized C3b which activates the alternative complement pathway
- Increased inflammatory response and efflux of fluid and leukocytes to the site of infection.
- Complement cascade lyses cells.
17
Q
S.pneumonia Diseases:
Pneumonia
A
- Fluid from inflammation response is rich in nutrients for bacterial growth.
- Bacterial growth in turn activates increased inflammation response.
18
Q
S.pneumonia Diseases:
Sinusitis and Otitis media
A
- Infections of the upper respiratory tract and inner ear.
- Usually preceded by viral infection of the upper respiratory tract
19
Q
S.pneumonia Diseases:
Bacteremia and Meningitis
A
- 25-30% of pneumococcal pneumonia patients develop bacteremia due S. pneumonia destruction and invasion of alveolar capillaries.
- Bacteremia can give access to the meninges, (membrane of brain and spinal cord)
- Infection and resulting inflammation are refered to as Meningitis
